A recovery core that looks right on paper can still underperform in the field. Bypass dampers leak, wheels rotate the wrong way, plates foul, and frost bypasses stick open. Commissioning is the step that proves the installed effectiveness matches the specification before the contractor leaves, and it is where most wasted-energy problems are caught and corrected for free rather than discovered a year later on an inflated utility bill.
What to measure
You need four temperatures and two pressures. Place sensors on the supply inlet (outdoor), exhaust inlet (return), supply outlet and exhaust outlet, and measure static pressure drop across both airstreams. In winter heating recovery the sensible effectiveness is:
eff = (T_supply_out - T_supply_in) / (T_exhaust_in - T_supply_in)
Measure flows with a pitot-tube traverse in straight duct or a balometer at the terminal, and confirm they are within 10% of design. Compare the measured effectiveness and pressure drop to the rated datasheet values at the actual face velocity, because effectiveness is only valid at the velocity the core was tested at, not at the catalogue headline.
Sensor placement and accuracy
Temperature sensors must sit in a straight duct run at least three diameters from any bend, damper or diffuser, and they should be averaged probes rather than a single point, because velocity profiles in large ducts are far from uniform. Use calibrated Type-T or better elements with a stated accuracy of +/-0.3 degrees C or tighter; a 1 degree C error on a 30 degree C recovery swing is a 3-point effectiveness error, enough to fail a borderline unit. Log at one-minute intervals for a full duty cycle so you capture both the design-day peak and the part-load behaviour the building actually lives in most of the time.
| Parameter | Design | Measured | Pass / fail |
|---|---|---|---|
| Sensible effectiveness | 80% | __% | within 5% of rated |
| Supply pressure drop | 180 Pa | __ Pa | within 10% of rated |
| Exhaust pressure drop | 160 Pa | __ Pa | within 10% of rated |
| Supply airflow | 10,000 m3/h | __ m3/h | within 10% of design |
Common field failures
- Leaking bypass damper drops effectiveness 15% to 30%; verify it is fully closed at part-load and that the actuator position agrees with the BAS.
- Wrong wheel rotation cuts recovery roughly in half; check direction against the nameplate and confirm the motor is energised.
- Fouled plates raise pressure drop 20% to 40% and lower recovery; schedule a wash per the maintenance plan before declaring the core faulty.
- Frost bypass stuck open in winter wastes all recovery; confirm it modulates only below the frost point and does not latch.
Acceptance, scheduling and handover
Accept the system when effectiveness is within 5% of rated at 90% design flow and pressure drop is within 10%. Document the numbers in a commissioning report so the payback calculation is based on real performance, not a brochure, and repeat the check at 12 months then every two to three years because cores drift as they foul. Where recovery is part of a retrofit business case, these measured values are the baseline the savings are claimed against, and an independent reviewer will ask for them. Start every project with the selection checklist so the commissioning targets are unambiguous from the outset.
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EN159 builds plate, rotary, heat-pipe and counterflow air-to-air exchangers for commercial, industrial and healthcare duty. Send airflow (m3/h), inlet temperatures and available space and we will size it.
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